Hi Nev,
E10 has been available in the US since 1990. Searching on the internet there are quite a few discussions on use of ethanol and E10 by
Mustangs with one referencing a users manual from 1990 recomending using E10. I found one on the Ford user manual site for 1996 model saying the same
but this was for a 4.6 litre model. I suspect that we can use E10 without any problems (10% ethanol) but I will also stick to E5 (98 octane) until I see something
definitive.
On another note when E85 (85% ethanol) was introduced here in Sweden cars, such as the SAAB 9-5 Bio power models, had a shorter service interval running on E85
than if they were run on E5. Ethanol affected the engine oil and oil filter lifetime apparently. My daughter drives such a model and it runs without any problems,
whatever petrol she tanks with.
The US Mustang oil change interval is 5000 miles according to the user manual I downloaded, the Ace is 6000 miles,
is the difference between the two taking into account the use of E10 petrol?
As I do a low milage I service my car on a yearly basis before putting it into winter storage I'm not too worried by this aspect either.
BR /Paho